Hence, metric learning is usually applied in the computer vision area, in which a deep transfer metric learning method for cross-domain visual recognition was proposed [1]}. Because of its ability to measure the latent relations between users and items, metric learning is also widely used in recommender systems. CML [2]} directly uses metric learning to embed the relationships between users and items. And IML [3]} proposes a practical framework to accelerate the learning process. In a word, metric learning has shown great potential to improve the relation representation.
